In The News: Paralysis Tied to Virus in Kids Goes Off-Script, Baffling CDC

Medpage Today reports on the missing surge in acute flaccid myelitis (AFM) it expected to see following its Health Alert Network Advisory in September on the rise in EV-D68. At the time, 17.4% of the children and adolescents who had reported acute respiratory illness seeking emergency care or hospitalization tested positive for EV-D68. That rate would rise to 56% by mid-August. The even year cycle prompted an expected spike that did not come, similar to 2020.

The lead of CDC’s Division of Viral Diseases observes this is the first year with such a large disconnect between EV-D68 and AFM since the association has been tracked beginning in 2014. The number of cases for 2022 is more representative of an off-year case number. The CDC continues to monitor the situation and is prepared to act if the spike should occur, though the regular circulation of enteroviruses would suggest there will not be a rise in AFM this year.

Prior to the outbreak of the COVID-19 pandemic in 2020, AFM cases in even years since the CDC began tracking ran from 120 in 2014 to 153 in 2016 to 238 in 2018. That compared to odd year cases between two to three dozen those years. During the even number pandemic years, cases have reached 33 in 2020 and 30 in 2022.

Masking and other pandemic mitigation efforts have been credited with the lower incidence of RSV and flu, and could be a factor here as well. Questions have also arisen as to whether the biennial pattern was accurately predictive. CDC intends to continue collecting data and comparing cases from previous years in hopes of furthering their understanding of AFM.

PIDS member Matthew Vogt, who studies EV-D68, commented, “Why the disconnect between EV-D68 infections and AFM cases in 2022? The easiest culprit to blame would be a mutation in the virus, but that is the one factor that seems an unlikely explanation based on initial research. The virus sequences from 2022 cluster very closely with the EV-D68 isolates from 2018, when a big spike in AFM was observed. My best guess is that something about the hosts changed, because clearly the pandemic changed normal patterns of disease due to many respiratory viruses. While entirely hand-waving, I suspect the context of other viruses raging through the community is what changed the hosts. We have much to learn here.”